Currently, approximately 90 percent of the world's power (˜1013 Watts or 10 TW) is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 percent efficiency, such that roughly 15 TW of heat is lost to the environment. Thermoelectric modules can potentially convert this low-grade waste heat to electricity, which could result in significant fuel savings and reduction in carbon emissions. Their efficiency depends on the thermoelectric figure of merit (ZT) of their material components, which is defined as ZT=S2σT/k where S, σ, k, and T are the Seebeck coefficient, electrical conductivity, thermal conductivity and absolute temperature, respectively. Over the past five decades, however, it has been challenging to increase ZT>1, since the parameters of ZT are generally interdependent. Nanostructured thermoelectric materials based on compounds of Bi, Te, Pb, Sb, and Ag have already been shown to increase ZT>1.
U.S. Pat. Nos. 6,882,051 and 6,996,147 disclose one-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These nanostructures include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions.